Have not fooled with any of the big m4's but a 5.25 on the smaller chargers even with the 7.5 lower would be utterly gutless on a 555 . Thats a huge upper pulley for a procharger.prob would never slip though for shure

What SC is that using?

M3 and M4 SC are big blowers for big airflow and power.

It's an M4 Non self contained...

Sucks that Procharger doesn't publish compressor maps. Their tech guys say to figure it as a direct equation to max output and you'll be close...

So, in my case with a 7.5 crank and 5.25 blower pulley and a 4.44:1 step up ratio it puts me at 36,789 impeller speed at 5800 rpm...

The blower is rated at 2500 CFM at 48,000 rpm, so at 36,789 rpm it should produce about 1916 CFM ...

Here is a good site to compare different Procharger supercharger outputs and pulleys and projected boost. Fun to play with.

http://zero2sixtymotorsports.com/pro...st-calculator/

Unfortunately it doesn't have the M4 supercharger listed.
With these big blowers, output is not linear. They are relatively inefficient at lower blower rpm's in making boost. It is a logarithmic increase.
So 3/4 rpm is not 3/4 cfm and hence boost. 36,789/48,000 x 2500cfm -- Does NOT equal 1916cfm but something much less.
It will also depend on your choice of TB/carb, intake manifold, heads, cam and all their flow ratings.

I suspect your pulley combination will possibly yield lower boost numbers than you think especially if all your other components are optimized.
No big deal, So you will just need a smaller SC pulley to achieve your boost target.
Procharge is playing is safe and very conservative. "Start low, Go slow" and proceed from there.

What kind of power do you expect?
Predictions--> 555 CID x 1.15hp/cid = 640hp x 8pounds boost(8/16) = 950hp, x 10pounds boost(10/16) = 1040hp if everything is optimized.
So how much CFM is needed for 1000hp?

When will you be building your engine?

I'm sort of a newbie when it comes to tuning, but can you really run 10 lbs of boost on 91 octane? I always thought you needed 1 more octane for every pound of boost?
Am curious for my own application too. I run 91 octane. 540 with v4 race vortec charger, electromotive ecu, 72 lbs injectors (mulitport). I pull 6lbs at 5000 rpm and thought I was making 775hp. So to get more hp, I can run a bigger pulley, larger injectors and flash ecu? I've got dart pro 1s, je pistons, calles crank, Carrillo rods, 741 cam. And be safe on 91?

Depends on base compression, cam, fuel and timing curve etc. I run 13 psi in my 540 on 93 octane, and did some dyno pulls on 92 octane BUT i went with dished blower pistons ( 8.3/ 8.4 compression) and they are swain tech coated on skirts,and crowns

does the electromotive ecu have the ability to run a knock sensor.thats what I would be looking at.you can use the afr meter but its tricky trying to see the knock events.

775 is a lot of power and wanting more. What drives are your using?

Your injectors are plenty big and you could easily make 100 200 more horsepower if you have enough boost and run some more rpms

I have 02 sensors, but I believe knock is supported . Can run closed or open loop as well. I have Huber 1350 trannies and SSM3s. Data logging is part of it too. Incidentally I need to retune since it looks like I'm a little lean (just did top ends and some valves were toast ).